<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="./jquery-3.7.1.min.js"></script>
</head>
<body>
    <div id="root">hello,学习jq</div>

    <script>
        $('#root').html('jQuery修改内容');

    </script>
</body>
</html>